Ross Finnie told the Scottish Parliament on Wednesday that sheep were no longer grazing around Loch Katrine, which supplies water to Glasgow.

But his Scottish National Party opponent Nicola Sturgeon told the minister that Scottish Water had issued a statement that afternoon confirming that 3,000 animals were still on the shore.

He is no longer in control of his brief and we can no longer trust a word that he says

Bruce Crawford SNP spokesman

Mr Finnie later told a media conference that he was "extraordinarily embarrassed" by his mistake.

The SNP is now calling on Mr Finnie to quit.

Environment spokesman Bruce Crawford said: "He is no longer in control of his brief and we can no longer trust a word that he says.

"The question is how long can this go on? First Minister Jack McConnell must remove him immediately from his ministerial responsibilities."

Tory environment spokesman John Scott added: "I think this characterises the executive's whole attitude to this crisis.

'English prat'

"They don't appear to be well enough informed to know what to do about it."

Mr Finnie's apology was his second in the space of three days.

On Sunday, he said sorry to Digby Brown, the head of the CBI, after calling him an "English prat".

The minister made the remark following a speech in Glasgow in which Mr Jones said the Scottish Executive must do more to assist business.

I want to make it absolutely clear that the executive is determined to learn whatever lessons arise from the recent incidents in Glasgow and Edinburgh

Ross Finnie

Mr Finnie had been attempting to reassure the public about the safety of the Scottish water supply during Wednesday's debate.

An outbreak of the cryptosporidium parasite in the water supply to parts of Glasgow and Clydebank last month affected more than 150,000 people.

They were advised to boil their supplies because of higher than normal levels of the parasite in water from Mugdock Reservoir in Milngavie, East Dunbartonshire.

Mr Finnie quoted a report from the Drinking Water Regulator, which found no evidence of mismanagement.

He said the responses of the incident control teams were "examples of the system working".

Learn lessons

And he said that the current regime ensured that the water industry operated in a way that provided the best possible protection for public health.

"Nevertheless, I want to make it absolutely clear that the executive is determined to learn whatever lessons arise from the recent incidents in Glasgow and Edinburgh and act upon them promptly and effectively, a process driven by the paramount importance of public health," he said.

Mr Finnie also told MSPs that he accepted there were "serious shortcomings" in the way information was handled in both cases.

He said that the incident in Edinburgh had been caused by a problem with the filtration system.

Thousands of people had to boil water

"There was very obvious confusion through the issuing first of a press statement alerting the public to the fact that cryptosporidium had been detected, followed by a subsequent statement confirming that no action was necessary," he told MSPs.

Mr Finnie said Scottish Water had recommended measures to avoid a similar situation in future.

"I have also asked the water industry commissioner, who has a particular responsibility for consumers, to look at all aspects of the way in which information was provided to Scottish Water's customers in Glasgow," he added.

The commissioner, Alan Sutherland, held a meeting in Glasgow on Tuesday night to seek residents' views, and will meet the people of Clydebank on Thursday evening.

Wednesday also saw the publication of a report by an ad hoc ministerial group set up by First Minister Jack McConnell.

It contained eight recommendations, including the appointment of a new advisor on cryptosporidium, a review of drinking water regulations and the production of an all-Scotland incident plan by December.